The invention relates to a 3dB waveguide directional coupler of the type in which two coupling slits or windows are spaced apart in a wall which is shared in common by two rectangular waveguides, the length of the common wall being the larger dimension of the cross-section of both rectangular waveguides. Such waveguide couplers are used to divide the total energy into equal part energies, a further division being possible by series arrangement of a plurality of waveguide couplers. The energy flow of such directional couplers is also reversible so that part energies can be combined. Such energy division or combination frequently is necessary when several transmitters of the same power and frequency are to be connected to a common load, generally an antenna.
In the known 3dB waveguide directional couplers the coupling slits or windows are disposed with the spacing .lambda.H/4 in the common or adjacent wide sides of the two waveguides, i.e. the coupling plane extended in the plane of said wide sides. The entire energy is then divided into a portion which is propagated over the same waveguide and a second portion which is propagated as a sum of the coupled-out fractions in the same direction in the adjacent waveguide. The portion of the adjacent waveguide next to the input of the waveguide receives the difference of the values and consequently the coupler is decoupled at this point.
This means that on connecting together the energy is supplied to the two adjacent terminals of the two waveguides and the entire energy must be carried off at the opposite end. This results in difficulties when connecting together transmitters arranged adjacent each other in a row because the supply to the directional couplers requires deviating lines which result in undesirably long leads.
The invention is thus based on the problem of providing a 3dB waveguide directional coupler of the aforementioned type which in a compact space permits connection of a plurality of transmitters arranged adjacent each other in a row.